1. Field of the Invention
The present invention relates to machines for effecting a refining treatment of materials, and more particularly refining fibrous pulp materials for the manufacture of paper or paperboard.
2. Description of Prior Art
Present methods of refining paper stock, as it comes from the beaters, digesters, or other pulping machines, involve usually passing the stock between grinding or refining surfaces which break up the fibrous materials and effect some further separation and physical modification of the fibers.
Typical pulp refiners or grinders, such as disclosed in U.S. Pat. No. 3,371,873, have a rotating disk provided on one or both sides with annular refining surface means. The disk refining surfaces face non-rotating annular grinding surfaces and define refining zones in which the pulp is worked. The rotating disk and its refining surfaces are made of a relatively inflexible material, such as cast iron or ni-hard stainless steel. The non-rotating grinding surfaces are made of like material and rigidly mounted so as to resist the torque created by the rapidly rotating disk and the pressure on the pulp material passing through the refining zone gap. Axial adjustment of the refining zone gaps is effected by axial shifting of the shaft on which the disk is mounted.
These rigid disk refiners must be manufactured and assembled to exacting tolerances in order to rigidly set the refining zone gap widths. Because the structural loads applied during the refining process to the rigid disk are large, a bulky and extremely rugged design is necessary so that the refining surface relationships do not change under load. This results in the rigid disk refiners being very costly due to the necessarily close tolerance machining, the need for large quantities of high strength disk material, the bulky overall structure, the restricted machine capacity, and the excessive assembly time requirements.